There are two groups of muscles in the back of the forearm - a superficial group and a deep group. The superficial group contains 7 muscles that originate on the lateral epicondyle of the humerus and insert on the bones of the hand and fingers. They function to extend the wrist and fingers. The deep group contains 5 muscles that originate on the bones of the forearm and insert on the thumb and second finger. They function to supinate the forearm and extend the thumb.

2. There are two groups of muscles at
the back of forearm.
1. Superficial Muscle group
2. Deep Muscle group

3. There are seven muscles in the
superficial group.
1. Anconeus
2. Brachioradialis
3. Extensor carpi radialis longus
4. Extensor carpi radialis brevis
5. Extensor digitorum
6. Extensor digiti minimi
7. Extensor carpi ulnaris

4. Origin:
Lateral epicondyle of
humerus
Insertion:
Lateral and inferior to
olecranon process of ulna

5. Action:
1. Not a prime mover in any
joint action;
2. Assists in elbow extension
Nerve supply:
Radial nerve (C7, C8)

6. Origin:
Lateral supracondylar
ridge on the humerus
Insertion:
Styloid process of the
radius

7. Action:
Elbow flexion
Nerve supply:
Radial nerve (C5, C6)

8. Origin:
Supracondylar ridge of
humerus
Insertion:
Base of second
metacarpal

9. Action:
1. Wrist extension
2. Radial deviation
Nerve supply:
Radial nerve (C6, C7)

10. Origin:
Lateral epicondyle of
humerus
Insertion:
Base of third
metacarpal

11. Action:
Wrist extension
Nerve supply:
Radial nerve
(C6, C7)

12. Origin:
Lateral epicondyle
of the humerus
Insertion:
Base of distal
phalanx of the second
through fifth fingers

13. Action:
Extends all three joints of the
fingers (MCP, PIP, and DIP)
Nerve supply:
Radial nerve (C6, C7, C8)

14. Origin:
Lateral epicondyle of humerus
Insertion:
Base of distal phalanx of fifth
finger

15. Action:
Extends all three joints of fifth
finger (MCP, PIP, and DIP)
Nerve supply:
Radial nerve (C6, C7, C8)

16. Origin:
Lateral epicondyle of humerus
Insertion:
Base of fifth metacarpal

17. Action:
Wrist extension, ulnar deviation
Nerve supply:
Radial nerve (C6, C7, C8)

18. There are 5 muscles in the deep muscle
group.
1. Supinator
2. Abductor pollicis longus
3. Extensor pollicis brevis
4. Extensor pollicis longus
5. Extensor indicis

19. Origin:
Lateral epicondyle of
humerus and adjacent ulna
Insertion:
Anterior surface of the
proximal radius

20. Action:
Forearm supination
Nerve supply:
Radial nerve (C6)

21. Origin:
Posterior radius, interosseous
membrane, middle ulna
Insertion:
Base of the first metacarpal

22. Action:
Abducts thumb (CMC)
Nerve supply:
Radial nerve (C6, C7)

23. Origin:
Posterior distal radius
Insertion:
Base of the proximal
phalanx of thumb

24. Action:
Extends CMC and MCP
joints of thumb
Nerve supply:
Radial nerve (C6, C7)

25. Origin:
Middle posterior ulna and
interosseous membrane
Insertion:
Base of distal phalanx of
thumb

26. Action:
Extends all three joints of the
thumb (CMC, MCP, and IP)
Nerve supply:
Radial nerve (C6, C7, C8)

27. Origin:
Distal ulna
Insertion:
Base of distal phalanx
of the second finger

28. Action:
Extends all three joints of
the second finger (MCP, PIP, and
DIP)
Nerve supply:
Radial nerve (C6, C7, C8)